We are using a genetic analysis to study female gametophyte envelopment in maize. The male and female gametes of plants are produced by haploid gametophytes that alternate generations with the diploid sporophyte, the dominant phase of the plant life cycle in angiosperms. After meoisis, the megagametophyte, or embryo sac, is produced by a small number of mitotic divisions and consists of four distinct cells-die egg cell, the central cell, the synergid cell, and the antipodal cell-in characteristic positions within the embryo sac. I propose to identify the developmental defects in embryo sac mutants using confocal microscopy to elucidate the role of the wild-type genes in megagametophyte development.